JP5683941B2 - Method for producing binder composition for mold making - Google Patents

Description

  The present invention relates to a method for producing a binder composition for mold making containing a furan resin, and a binder composition for mold making.

  Acid-curing self-hardening mold is a hardened material containing a self-hardening mold-forming binder containing acid-hardening resin such as furan resin, and phosphoric acid, organic sulfonic acid, sulfuric acid, etc. An agent is added and these are kneaded, and then the obtained kneaded sand is filled in an original mold such as a wooden mold and the acid curable resin is cured.

  Examples of the furan resin include furfuryl alcohol, furfuryl alcohol / urea formaldehyde resin, furfuryl alcohol / formaldehyde resin, furfuryl alcohol / phenol / formaldehyde resin, and other known modified furan resins.

  The furan resin is usually obtained by polymerizing a monomer composition containing furfuryl alcohol in the presence of an acid catalyst. As the acid catalyst, hydrochloric acid, sulfuric acid, phosphoric acid, xylene sulfonic acid, glutaric acid, succinic acid and the like are used. When the furan resin obtained using the acid catalyst is used in a binder composition, condensation of the furan resin proceeds by the acid catalyst remaining in the binder composition. Viscosity increases. In particular, when the storage temperature is high, the increase in viscosity becomes significant. When the binder composition having increased viscosity after storage is used for molding a mold, there has been a problem that the pot life during mold molding is shortened. Moreover, since the supply by the pump becomes unstable, kneading unevenness is caused, and as a result, there is a problem that the strength of the obtained mold is lowered.

  Further, since the furan resin is acidic and the reaction proceeds, there is a method of preventing the increase in viscosity by adding an alkali to adjust the pH of the binder composition to 7 or more neutral to alkaline. However, when an alkali is added to the binder composition, a part of the acid that is a curing agent is subjected to a neutralization reaction with the added alkali at the time of mold molding, and the mold may be cured slowly. was there. Furthermore, since a neutralized salt is generated in the binder composition, the ratio of the resin component (pure component) is reduced, and the mold strength may be reduced.

  On the other hand, a technique using a solid acid catalyst when synthesizing a furan resin is known. For example, Patent Document 1 below describes a method of synthesizing a furan resin for a binder composition using an ion exchange resin containing a sulfonic acid group. Non-Patent Document 1 below describes a method of synthesizing a furan resin for a binder composition using a carbon-based solid acid in which sulfonic acid groups are introduced by allowing sulfuric acid to act on carbon.

JP-A-55-82117

Saitama Industrial Technology Center Research Report Vol. 6 (2008) "Development of environmentally friendly mold making method"

  Since the solid acid catalyst can be removed by filtration or the like after synthesis, the problem caused by the remaining acid catalyst can be solved. However, since the solid acid used in Patent Document 1 and Non-Patent Document 1 is a strong acid containing a sulfonic acid group, a local reaction occurs on the catalyst surface during the synthesis of the furan resin depending on conditions, and the resin on the catalyst surface. It became clear by examination of this inventor that this will harden | cure. When the resin is cured on the catalyst surface, the solid acid catalyst does not function as a reaction catalyst, so that the intended reaction cannot be stably performed, and a desired furan resin cannot be produced.

  The present invention can easily synthesize a furan resin for a binder composition, suppress the increase in viscosity of the binder composition, and prevent the resulting mold from being reduced in strength. The manufacturing method of an agent composition and the binder composition for mold making are provided.

  The method for producing a binder for mold making according to the present invention is a method for producing a binder composition for mold making containing a furan resin, wherein Hammett's acidity function Ho is 3.3 or more. It is a method for producing a binder composition for mold making, comprising a step of polymerizing a monomer composition containing furfuryl alcohol in the presence of a catalyst and then removing the solid acid catalyst to obtain the furan resin.

  The binder composition for mold making of the present invention is a binder composition for mold making obtained by the production method of the present invention.

  According to the method for producing a binder composition for mold making of the present invention, it is possible to easily synthesize a furan resin for a binder composition, and to suppress an increase in the viscosity of the binder composition, The binder composition for mold making which can prevent the intensity | strength fall of the obtained casting_mold | template can be manufactured. Moreover, according to the binder composition for mold making of this invention, the viscosity raise of a binder composition can be suppressed and the intensity | strength fall of the casting_mold | template obtained can be prevented.

  The manufacturing method of the binder composition for mold making of the present invention (hereinafter, also simply referred to as “binding agent composition”) is directed to the manufacturing method of a binder composition containing a furan resin. In the present invention, a monomer composition containing furfuryl alcohol is polymerized in the presence of a solid acid catalyst having a Hammett acidity function Ho (hereinafter also simply referred to as “Ho”) of 3.3 or more. As described above, in the present invention, since a weak acid having Ho of 3.3 or more is used, a local reaction hardly occurs even with a solid acid catalyst, and the resin can be synthesized uniformly. In addition, Ho in the present invention is an index of acid strength measured using a Hammett indicator, and indicates that a larger value indicates a weaker acid. The upper and / or lower limit of the numerical range is determined by the Hammett indicator pKa. An example of a specific method for measuring Ho will be described in Examples described later.

  In the present invention, it is essential that Ho is 3.3 or more from the viewpoint of preventing local reaction, and Ho is preferably less than 6.8 from the viewpoint of improving the polymerization rate, and less than 4.8. Is more preferable, and it is still more preferable that it is less than 4.0. That is, in the present invention, Ho is preferably 3.3 or more and less than 6.8, and more preferably 3.3 or more and less than 4.8 from the viewpoint of achieving both prevention of local reaction and improvement of the polymerization rate. Preferably, it is 3.3 or more and less than 4.0.

  Moreover, in this invention, after superposing | polymerizing a monomer composition, a solid acid catalyst is removed and a furan resin is obtained. Examples of the removal method include filtration, centrifugation, and decantation. Thus, since a solid acid catalyst is used in the present invention, the catalyst can be easily removed after the synthesis of the furan resin. Thereby, the viscosity raise of the binder composition resulting from an acid catalyst can be suppressed. Furthermore, since it is not necessary to adjust the pH of the binder composition by adding alkali, there is no formation of a furan resin neutralized salt, and the proportion of the resin component (pure component) in the binder composition is increased. be able to. Therefore, according to the present invention, it is possible to prevent a reduction in strength of the obtained mold. The “solid acid catalyst” is a catalyst composed of an acid that is solidly dispersed in the reaction solution, and refers to an acid that is difficult to dissolve in the furan resin during and after the synthesis of the furan resin. This refers to an acid having a solubility of 10 mg or less with respect to 100 g of the synthesized furan resin.

  The solid acid catalyst that can be used in the present invention is not particularly limited as long as Ho is 3.3 or more. For example, a solid acid containing a carboxyl group, silanol group, hydroxyl group or the like as a functional group, or a Lewis acid point on the surface. From the viewpoint of preventing a reduction in the strength of the template, a solid acid containing a carboxyl group and a solid acid containing a silanol group are preferred, and a solid acid containing a carboxyl group is more preferred.

  Specific examples of the solid acid having Ho of 3.3 or more include an ion exchange resin containing a carboxyl group and an oxide such as silica gel. Moreover, in order to adjust Ho, the solid acid surface may be chemically modified and adjusted. Illustrative examples of the ion exchange resin include Amberlite IRC-50 and Amberlite IRC-76 manufactured by Organo Corporation. Examples of the silica gel include silica gel 4B manufactured by Fuji Devison Chemical Co., Ltd.

  The furan resin synthesized using the solid acid catalyst is not particularly limited as long as it is obtained by polymerizing a monomer composition containing furfuryl alcohol and can be used as a binder for mold making. For example, condensates of furfuryl alcohol, condensates of furfuryl alcohol and aldehydes, condensates of furfuryl alcohol and urea, condensates of furfuryl alcohol and phenols and aldehydes, furfuryl alcohol and melamine and aldehydes. A condensate, one or more selected from the group consisting of furfuryl alcohol, urea and aldehydes, or a cocondensate consisting of two or more selected from the above group can be used. Among these, from the viewpoint of improving the flexibility of the obtained mold and the improvement of the mold strength, a condensate of furfuryl alcohol and urea, a condensate of furfuryl alcohol, melamine and aldehydes, furfuryl alcohol and urea. Condensates of aldehydes are preferable, and condensates of furfuryl alcohol, urea, and aldehydes are more preferable. Note that the binder composition obtained from a compound having an amino group such as urea or melamine is considered to form a crosslink bond with the resin component, and this has a favorable effect on the flexibility and strength of the obtained mold. Guess to give. The flexibility of the mold is necessary when the mold is extracted from the original mold. In particular, when a mold having a complicated shape is formed, if the mold has high flexibility, it is possible to prevent mold cracks caused by stress concentration at a portion where the thickness of the mold is thin at the time of mold removal.

  In the synthesis of furan resin, unreacted furfuryl alcohol usually remains. The furan resin synthesized using the solid acid catalyst is further mixed with furfuryl alcohol from the viewpoint of adjusting the viscosity of the binder composition to an appropriate range when used in the binder composition. May be. That is, the binder composition obtained by the production method of the present invention can contain furfuryl alcohol in addition to the furan resin synthesized using the solid acid catalyst.

  The monomer composition used for the synthesis of the furan resin is selected according to the desired condensate, and contains, for example, one or more monomers selected from furfuryl alcohol, aldehydes, urea, phenols, and melamine. Monomer compositions can be used.

  Examples of the aldehydes include formaldehyde, acetaldehyde, glyoxal, furfural, terephthalaldehyde, and hydroxymethylfurfural, and one or more of these can be used as appropriate. From the viewpoint of improving the mold strength, it is preferable to use formaldehyde, and from the viewpoint of reducing the amount of formaldehyde generated during molding, it is preferable to use furfural, terephthalaldehyde, or hydroxymethylfurfural.

  Examples of the phenols include phenol, cresol, resorcin, bisphenol A, bisphenol C, bisphenol E, and bisphenol F, and one or more of these can be used.

  When manufacturing the condensate of furfuryl alcohol and aldehydes, it is preferable to use 0.01-1 mol of aldehydes with respect to 1 mol of furfuryl alcohol. Moreover, when manufacturing the condensate of furfuryl alcohol, aldehydes, and urea, 0.05-3 mol of aldehydes and 0.03-1.5 mol of urea are used with respect to 1 mol of furfuryl alcohol. It is preferable to do.

  The weight ratio of the monomer composition to the solid acid catalyst when synthesizing the furan resin is appropriately adjusted from the viewpoint of the reaction method, the specific gravity of the solid acid catalyst used, or shortening the production time. In the case of polymerization in a solid acid suspension, the weight ratio is preferably a reaction solution containing a monomer composition: a solid acid catalyst = 100: 0.1 to 100: 50, preferably 100: 5 to 100: 30. Is more preferable, and 100: 10 to 100: 20 is even more preferable. Moreover, it can also be made to react by distribute | circulating a reaction liquid in the fixed bed filled with the solid acid.

  The reaction temperature when synthesizing the furan resin varies depending on the raw material used. The viscosity of the binder composition obtained after the reaction, the residual amount of aldehyde, shortening the production time, preventing the runaway reaction of the furan resin, and the evaporation of the raw material From the viewpoint of prevention, 50 to 150 ° C is preferable, 70 to 130 ° C is more preferable, and 80 to 130 ° C is still more preferable. From the same viewpoint, the reaction time for synthesizing the furan resin is preferably 0.5 to 12 hours, more preferably 1 to 10 hours, and further preferably 3 to 8 hours.

  The furan resin synthesized using the solid acid catalyst is used as one component of the binder composition, but the content of the synthesized furan resin in the binder composition is the viscosity during storage. From the viewpoint of preventing the increase, the content is preferably 5% by weight or more, more preferably 30% by weight or more, and further preferably 50% by weight or more.

  When the binder composition obtained by the production method of the present invention contains furfuryl alcohol, from the viewpoint of adjusting the viscosity of the binder composition to an appropriate range, furfuryl in the binder composition. The alcohol content is preferably 50 to 98% by weight, more preferably 60 to 90% by weight, and still more preferably 70 to 85% by weight.

  In the present invention, after removing the solid acid catalyst, one or more selected from urea and melamine, an aldehyde and an alkali catalyst may be added to the reaction solution, and a polymerization reaction may be further performed to obtain a furan resin. . By using an alkali catalyst, the reaction of one or more selected from urea and melamine, aldehydes, and a furfuryl alcohol condensate or cocondensate can be promoted. In addition, since urea and melamine are amino group-containing compounds, co-condensation with a furyl alcohol condensate or co-condensate can improve the mold flexibility and the mold strength.

  As the alkali catalyst, potassium hydroxide, sodium hydroxide, calcium hydroxide, magnesium hydroxide or the like can be used. The alkali catalyst to be added is about 0.01 to 2 parts by weight with respect to 100 parts by weight of one or more compounds selected from urea and melamine.

  The reaction temperature when polymerizing using the above alkali catalyst is the viewpoint of the viscosity of the binder composition obtained after the reaction, the residual amount of aldehyde, shortening the production time, preventing the runaway reaction of furan resin, and preventing the evaporation of raw materials. Therefore, 50 to 160 ° C is preferable, 70 to 140 ° C is more preferable, and 80 to 110 ° C is still more preferable. From the same viewpoint, the reaction time is preferably 5 to 600 minutes, more preferably 10 to 180 minutes, and still more preferably 30 to 120 minutes.

  Next, each component contained in the binder composition for mold making of the present invention (binder composition) will be described. The binder composition of the present invention is a binder composition obtained by the above-described production method of the present invention, that is, a binder composition containing a furan resin synthesized using the solid acid catalyst. is there. Therefore, since the content regarding furan resin overlaps with the above, it is omitted.

<Curing accelerator>
The binder composition of the present invention may contain a curing accelerator from the viewpoint of preventing cracking of the mold and improving the final mold strength. As the curing accelerator, from the viewpoint of improving the final mold strength, a compound represented by the following general formula (1) (hereinafter referred to as curing accelerator (1)), a phenol derivative, an aromatic dialdehyde, and tannin. One or more selected from the group consisting of categoricals is preferred.

〔式中、Ｘ₁及びＸ₂は、それぞれ水素原子、ＣＨ₃又はＣ₂Ｈ₅の何れかを表す。〕

[Wherein, X ₁ and X ₂ each represent a hydrogen atom, CH ₃ or C ₂ H ₅ . ]

  As the curing accelerator (1), 2,5-bishydroxymethylfuran, 2,5-bismethoxymethylfuran, 2,5-bisethoxymethylfuran, 2-hydroxymethyl-5-methoxymethylfuran, 2-hydroxy Examples include methyl-5-ethoxymethylfuran and 2-methoxymethyl-5-ethoxymethylfuran. Among these, 2,5-bishydroxymethylfuran is preferably used from the viewpoint of improving the final template strength. The content of the curing accelerator (1) in the binder composition is 0.5 to 0.5 from the viewpoint of the solubility of the curing accelerator (1) in the furan resin and the final mold strength. It is preferably 63% by weight, more preferably 1.8 to 50% by weight, still more preferably 2.5 to 50% by weight, still more preferably 3.0 to 40% by weight. preferable.

  Examples of the phenol derivative include resorcin, cresol, hydroquinone, phloroglucinol, methylene bisphenol, and the like. Among these, resorcin is preferable from the viewpoint of deep moldability of the mold and the viewpoint of improving the final mold strength. The content of the phenol derivative in the binder composition is preferably 1 to 25% by weight from the viewpoint of the solubility of the phenol derivative in the furan resin and the final mold strength. It is more preferably 2 to 15% by weight, and further preferably 3 to 10% by weight. In particular, when resorcin is used, the content of resorcin in the binder composition is 1 to 10% by weight from the viewpoint of the solubility of resorcin in the furan resin and the final mold strength. Preferably, it is 2 to 7% by weight, more preferably 3 to 6% by weight.

  Examples of the aromatic dialdehyde include terephthalaldehyde, phthalaldehyde, isophthalaldehyde, and derivatives thereof. These derivatives mean compounds having a substituent such as an alkyl group on the aromatic ring of an aromatic compound having two formyl groups as the basic skeleton. From the viewpoint of preventing cracking of the mold, terephthalaldehyde and terephthalaldehyde derivatives are preferable, and terephthalaldehyde is more preferable. The content of the aromatic dialdehyde in the binder composition is preferably 0.1 to 0.1 from the viewpoint of sufficiently dissolving the aromatic dialdehyde in the furan resin and suppressing the odor of the aromatic dialdehyde itself. It is 15% by weight, more preferably 0.5 to 10% by weight, still more preferably 1 to 5% by weight.

  Examples of tannins include condensed tannins and hydrolyzed tannins. Examples of these condensed tannins and hydrolyzed tannins include tannins having a pyrogallol skeleton and a resorcin skeleton. Moreover, you may add the extract from natural products, such as a leaf bark extract containing these tannins, and a leaf derived from a plant, a fruit, a seed | species, and a worm hump parasitic on a plant.

<Moisture>
The binder composition of the present invention may further contain moisture. For example, when synthesizing various condensates such as a condensate of furfuryl alcohol and aldehydes, an aqueous raw material is used or condensed water is generated. Therefore, the condensate is usually in the form of a mixture with moisture. It is obtained with. When using such a condensate in a binder composition, moisture may be removed by topping, etc., if necessary. However, as long as the curing reaction rate can be maintained, it is necessary to remove it during production. There is no. In addition, moisture may be further added for the purpose of adjusting the binder composition to a viscosity that is easy to handle. However, since excessive moisture may inhibit the curing reaction of the furan resin, the water content in the binder composition is preferably in the range of 0.5 to 30% by weight. From the viewpoint of making the agent composition easy to handle and maintaining the curing reaction rate, the range of 1 to 10% by weight is more preferable, and the range of 3 to 7% by weight is more preferable. Further, from the viewpoint of improving the final mold strength, it is preferably 10% by weight or less, more preferably 7% by weight or less, and still more preferably 4% by weight or less.

<Other additives>
The binder composition may further contain an additive such as a silane coupling agent. For example, it is preferable that a silane coupling agent is included because the final mold strength can be improved. Examples of silane coupling agents include N-β (aminoethyl) γ-aminopropylmethyldimethoxysilane, N-β (aminoethyl) γ-aminopropyltrimethoxysilane, N-β (aminoethyl) γ-aminopropyltriethoxy. Aminosilanes such as silane, 3-aminopropyltrimethoxysilane, 3-glycidoxypropyltrimethoxysilane, 3-glycidoxypropyltriethoxysilane, 3-glycidoxypropylmethyldiethoxysilane, 3-glycidoxy Epoxy silanes such as propyltriethoxysilane, alkoxy silanes such as γ-propyltriethoxy silane, ureido silane, mercapto silane, sulfide silane, methacryloxy silane, acryloxy silane and the like are used. Amino silane, epoxy silane, and ureido silane are preferable. The content of the silane coupling agent in the binder composition is preferably 0.01 to 0.5% by weight, and 0.05 to 0.3% by weight from the viewpoint of improving the final mold strength. % Is more preferable.

  Further, in the self-hardening mold, since the reaction is started immediately after mixing the refractory particles, the binder composition and the curing agent in the mixer, the viscosity of the binder composition is preferably low. From the above viewpoint, the viscosity of the binder composition of the present invention is preferably 1 to 80 mPa · s, more preferably 5 to 60 mPa · s, as a value measured with an E-type viscometer at 25 ° C. More preferably, it is 8 to 40 mPa · s.

  The binder composition of the present invention is suitable for a mold manufacturing method in which kneaded sand is prepared by kneading together with refractory particles and a curing agent, and the kneaded sand is cured. When a mold is produced using the binder composition of the present invention, a conventional process for producing a mold can be applied. For example, by adding the binder composition of the present invention and a curing agent for curing the binder composition to the refractory particles, and kneading them with a batch mixer or a continuous mixer, the kneaded sand is obtained. Can be obtained. In this case, it is preferable to add the binder composition of the present invention after adding the curing agent to the refractory particles.

  As the refractory particles, conventionally known ones such as silica sand, chromite sand, zircon sand, olivine sand, alumina sand, mullite sand, and synthetic mullite sand can be used. Processed ones can also be used.

  Examples of the curing agent include xylene sulfonic acid (especially m-xylene sulfonic acid), toluene sulfonic acid (particularly p-toluene sulfonic acid), sulfonic acid compounds such as methane sulfonic acid, phosphoric acid, acidic phosphoric acid ester and the like. One or more conventionally known compounds such as an acidic aqueous solution containing a phosphoric acid compound and sulfuric acid can be used. Further, the curing agent may contain one or more solvents selected from the group consisting of alcohols, ether alcohols and esters, and carboxylic acids. Among these, alcohols and ether alcohols are preferable and ether alcohols are more preferable from the viewpoint of improving the final mold strength. Moreover, when the said solvent and the said carboxylic acid are contained, since the moisture content in a hardening | curing agent is reduced, final mold intensity | strength further improves. The content of the solvent or the carboxylic acid in the curing agent is preferably 5 to 50% by weight and more preferably 10 to 40% by weight from the viewpoint of improving the final mold strength. Moreover, it is preferable to contain methanol and ethanol from a viewpoint of reducing the viscosity of a hardening | curing agent.

  From the viewpoint of improving the final mold strength, the alcohols are preferably propanol, butanol, pentanol, hexanol, heptanol, octanol, benzyl alcohol, and the ether alcohols include ethylene glycol monoethyl ether, ethylene Glycol monobutyl ether, ethylene glycol monohexyl ether, diethylene glycol monoethyl ether, diethylene glycol monobutyl ether, diethylene glycol monohexyl ether, diethylene glycol monophenyl ether, ethylene glycol monophenyl ether are preferred, and the esters include butyl acetate, butyl benzoate, Ethylene glycol monobutyl ether acetate, diethylene glycol monobutyl Ether acetate are preferred. As the carboxylic acids, a carboxylic acid having a hydroxyl group is preferable, and lactic acid, citric acid, and malic acid are more preferable from the viewpoint of improving the final template strength and reducing odor.

  The ratio of the refractory particles, the binder composition and the curing agent in the kneaded sand can be set as appropriate, but the binder composition is 0.5 to 1.5 parts by weight with respect to 100 parts by weight of the refractory particles. The curing agent is preferably in the range of 0.07 to 1 part by weight. With such a ratio, it is easy to obtain a mold having sufficient strength. Furthermore, the content of the curing agent is 10 to 40 weights with respect to 100 parts by weight of the furan resin in the binder composition from the viewpoint of minimizing the amount of water contained in the mold and the mixing efficiency in the mixer. Parts, preferably 15 to 35 parts by weight, more preferably 18 to 25 parts by weight.

  The mold forming binder composition of the present invention can be produced by diluting with furfuryl alcohol as necessary using the furan resin produced using the above solid acid, but the mold forming binder of the present invention. In the production of the agent composition, the curing accelerator can be mixed. Moreover, you may mix a silane coupling agent as another additive. That is, the binder composition for mold making of the present invention may be composed of a furan resin produced using the above solid acid, and the furan resin together with furfuryl alcohol, a curing accelerator, or other It may be a mixture with an additive or the like. Moisture may be removed by topping or the like, if necessary, but it is not necessary to remove it during production as long as the curing reaction rate can be maintained.

  Examples and the like specifically showing the present invention will be described below. In addition, the evaluation item in an Example etc. measured as follows.

<Ho of solid acid catalyst>
0.1 g of the solid acid catalyst was put in 10 mL of cyclohexane, and 2 drops of each 0.1 wt% Hammett indicator cyclohexane solution shown below were dropped, and the color change on the catalyst was observed. Hammett indicator is dicinnamalacetone (pKa-3.0) → 4-benzeneazodiphenylamine (pKa + 1.5) → p-dimethylaminoazobenzene (pKa + 3.3) → phenylazonaphthylamine (pKa + 4.0) → methyl red (pKa + 4) .8) → Neutral red (pKa + 6.8). In this case, for example, when p-dimethylaminoazobenzene (pKa + 3.3) is not colored in an acidic color and phenylazonaphthylamine (pKa + 4.0) is colored in an acidic color, Ho is 3.3 or more and 4 Judged to be less than 0.0. The other cases were similarly judged.

<PH of binder composition>
The pH of the binder composition was measured with a pH meter at 25 ° C. by mixing the binder composition, the binder composition and an equal weight of ion-exchanged water.

<Viscosity of binder composition>
About the obtained binder composition, after the synthesis | combination, after storing for 7 days at 50 degreeC, and after storing for 14 days at 50 degreeC, the viscosity in 25 degreeC was measured using the E-type viscosity meter (made by Tokyo Keiki Co., Ltd.). .

<Mold strength>
Under conditions of 25 ° C. and 50% RH, 8 kg of 60% by weight paratoluenesulfonic acid aqueous solution as a furan resin curing agent was added to 2 kg of Kaketsu Fusen No. 5 silica sand (manufactured by Yamakawa Sangyo Co., Ltd.) and kneaded. Then, 20 g of the binder composition after storage for 7 days was added and kneaded to obtain kneaded sand. The kneaded sand immediately after kneading was filled into a wooden frame of φ50 mm × height 50 mm, and after 5 hours from filling, the mold was removed, and the compressive strength was measured by the method described in JIS Z 2604-1976. The measured value was used as the mold strength.

(Example 1)
1000 parts by weight of furfuryl alcohol, 266 parts by weight of 92% by weight paraformaldehyde, and 102 parts by weight of ion exchange resin Amberlite IRC-50 (manufactured by Organo) as a solid acid catalyst were placed in a three-necked flask and stirred at 110 ° C. for 6 hours. While reacting. Thereafter, the reaction solution was cooled to 25 ° C. and allowed to stand to precipitate the solid acid catalyst, and then the reaction solution was taken out by decantation. To 456 parts by weight of the obtained reaction liquid, 0.1 part by weight of 92% by weight of paraformaldehyde, 53 parts by weight of urea, and 0.18 part by weight of 25% by weight of sodium hydroxide aqueous solution are added, and 100 ° C. for 30 minutes. The reaction was carried out with stirring. Thereafter, the reaction solution was cooled to 50 ° C., and further 45 parts by weight of ion exchange resin Amberlite IRC-50 was added and reacted at 100 ° C. for 30 minutes in the same manner. The reaction solution was cooled again to 25 ° C., 120 parts by weight of furfuryl alcohol was added and stirred, and then allowed to stand to settle the solid acid catalyst, and the solid acid catalyst was removed by decantation. 100 parts by weight of the reaction solution obtained was adjusted to pH 7.2 with a 48% by weight aqueous potassium hydroxide solution, and then 0.1 part by weight of γ-propyltriethoxysilane was added to obtain the binder composition of Example 1. It was. In addition, Amberlite IRC-50 used what was previously dried at 50 degreeC for 1 day.

(Example 2)
1000 parts by weight of furfuryl alcohol, 266 parts by weight of paraformaldehyde of 92% by weight, and 250 parts by weight of silica gel 4B (manufactured by Fuji Devison Chemical Co., Ltd.) as a solid acid catalyst were placed in a three-necked flask and reacted at 110 ° C. for 6 hours. Then, operation similar to the said Example 1 was performed, and the binder composition of Example 2 was obtained.

Example 3
1000 parts by weight of furfuryl alcohol, 266 parts by weight of 92% by weight paraformaldehyde, and 102 parts by weight of ion exchange resin Amberlite IRC-76 (manufactured by Organo) as a solid acid catalyst were placed in a three-necked flask and reacted at 110 ° C. for 6 hours. I let you. Then, operation similar to the said Example 1 was performed, and the binder composition of Example 3 was obtained.

Example 4
A binder composition of Example 4 was obtained in the same manner as in Example 1 except that the pH was not adjusted with a 48 wt% potassium hydroxide aqueous solution in Example 1.

(Comparative Example 1)
1000 parts by weight of furfuryl alcohol, 266 parts by weight of 92% by weight paraformaldehyde, and 48 parts by weight of succinic acid were placed in a three-necked flask and reacted at 110 ° C. with stirring for 6 hours. Thereafter, the reaction solution was cooled to 25 ° C. Next, 0.1 part by weight of 92% by weight paraformaldehyde, 53 parts by weight of urea, and 31 parts by weight of 25% by weight aqueous sodium hydroxide were added to 456 parts by weight of the reaction solution, and the mixture was stirred at 100 ° C. for 30 minutes. It was made to react. Thereafter, the reaction solution was cooled to 50 ° C., 10 parts by weight of succinic acid was further added, and reacted at 100 ° C. for 30 minutes. The reaction solution was cooled to 25 ° C., 120 parts by weight of furfuryl alcohol was added and stirred, and then 0.1 part by weight of γ-propyltriethoxysilane was added to obtain a binder composition of Comparative Example 1.

(Comparative Example 2)
1000 parts by weight of furfuryl alcohol, 266 parts by weight of paraformaldehyde of 92% by weight, and 102 parts by weight of ion exchange resin Amberlite CG-120 (manufactured by Organo) as a solid acid catalyst were placed in a three-necked flask and reacted at 110 ° C. However, since the resin was cured on the catalyst surface immediately after the reaction, a binder composition could not be obtained.

(Comparative Example 3)
1000 parts by weight of furfuryl alcohol, 266 parts by weight of paraformaldehyde of 92% by weight, and 102 parts by weight of zeolite A-3 (manufactured by Wako Pure Chemical Industries, Ltd.) as a solid acid catalyst were placed in a three-necked flask and reacted at 110 ° C. Since the resin was cured on the catalyst surface immediately after the reaction, a binder composition could not be obtained.

  About the obtained binder composition, each item was evaluated by the method mentioned above. The results are shown in Table 1.

  As shown in Table 1, in Examples 1 to 4, good results were obtained for any of the evaluation items. On the other hand, since the viscosity increased in Comparative Example 1 after storage at 50 ° C., the mold strength decreased. In Comparative Examples 2 and 3, as described above, since the resin was cured on the catalyst surface immediately after the reaction, a binder composition could not be obtained. From this result, according to the present invention, it is possible to easily synthesize a furan resin for a binder composition, and to suppress an increase in the viscosity of the binder composition and to prevent a reduction in strength of the obtained mold. It was confirmed that it was possible.

Claims (6)

A method for producing a binder composition for mold making containing a furan resin,
A step of polymerizing a monomer composition containing furfuryl alcohol in the presence of a solid acid catalyst having a Hammett acidity function Ho of 3.3 or more, and then removing the solid acid catalyst to obtain the furan resin. A method for producing a binder composition for mold making.   Furthermore, the manufacturing method of the binder composition for mold making of Claim 1 which has the process of obtaining the binder composition for mold making using the obtained furan resin.   The manufacturing method of the binder composition for mold making of Claim 1 or 2 whose said solid acid catalyst is 1 or more types chosen from the solid acid containing a carboxyl group, and the solid acid containing a silanol group.   The furan resin is a condensate of furfuryl alcohol, a condensate of furfuryl alcohol and aldehydes, a condensate of furfuryl alcohol and urea, a condensate of furfuryl alcohol, phenols and aldehydes, furfuryl alcohol and melamine. Condensates of aldehydes, and one or more selected from the group consisting of condensates of furfuryl alcohol, urea and aldehydes, or cocondensates consisting of two or more selected from the above group are included. The manufacturing method of the binder composition for mold making of any one of these. Furthermore, it has the process of adding the said silane coupling agent so that content of the silane coupling agent in the binder composition for mold making may be 0.01 to 0.5 weight%. The manufacturing method of the binder composition for mold making of any one of these. The binder composition for mold making obtained by the manufacturing method of any one of Claims 1-5 .